Method of separating electrodeposited layers



May 18, 1943 A, w, GRANT, 2,319,596

METHODOF SEPARATING ELECTRODEPOSITED LAYERS Filed April 3, 1940INVENTOR. 4/? 7 901? 144 6/?4/1 7' Ma-W ATTORNEY deposited iron from theoriginal pattern.

Patented May 18, 1943 UNITED STATES PATENT OFFICE METHOD OF SEPARATIN GELECTRO- DEPOSITED LAYERS Arthur W. Grant, Detroit, Micln, assignor toUnited States Rubber Company, New York, N. Y., a corporation of NewJersey Application April 3, 1940, Serial No. 327,604

2 Claims. This invention relates to electroforming of metals, and, inparticular, it relates to the electrodeposition of iron upon a metal ormetal coated pattern. More" particularly, the invention relates to thetreatment of a pattern prior to electrodeposition, in a manner toprovide proper separation of the deposited metal upon completion of theoperation.

In many cases in the electrodeposition of iron, it is desirable thatminute details be reproduced from the original pattern. This requireshigh fidelity in the reproduction operation and in the method used toprovide separation of the electro- In accordance with my invention, Ipropose to cover an original metal or metal coated pattern with a layerof copper which layer may be formed thereon by electrodeposition. Overthis layer a thin layer of silver is deposited. Thereafter the iron iselectrodeposited upon the surface of the silver. In separating the ironfrom the pattern, the point of separation lies between the silver andcopper deposits. In some cases the use of a layer of silver iodide as aseparating medium has been practiced, but such material is notapplicable to an iron plating solution as the ferrous ion reduces thesilver salt to metallic silver and destroys the film. The invention,therefore, contemplates the use of a layer of metallic silver.

Among the objects of my invention are: to provide separating meansbetween a metal or metal coated pattern and an electrodeposited body ofiron which may be easily parted'while maintaining minute details andsurface finish; to provide a separation layer which will prevent any ofthe electrolyte from flowing between the surfacesdefining the plane ofseparation; and, to 'provide a separation layer which may remain on thefinished electrodeposited body of iron. These and other objects andadvantages will appear more fully in the following detailed descriptionto be considered in connection with the accompanying drawing, in which:

Fig. 1 is a perspective view illustrating an original pattern;

Fig. 2 is a perspective view of the-original pattern illustrating alayer of copper deposited thereon;

Fig. 3 is a perspective view of the original pattern with the layer ofcopper and a layer of silver deposited thereon;

Fig. 4 is a perspective view of the original pattern, the separationlayers, and an electrodeposited body of iron formed against the surfaceof the deposited layer of silver; and,

Fig. 5 is a perspective view of the original pattern and the depositediron illustrating the plane of separation between the bodies.

Where the original pattern in an electroforming operation is composed ofa material which in itself is not an electrical conductor, various typesof conducting paints may be coated on the surface so as to render thepattern capable of receiving an electrod'epositing body of metal. Insuch cases the conducting paint itself serves as a means to facilitateseparation of the deposited metal from the original pattern. Adistinguished from this practice, the present invention refers to theuse of a pattern which, in itself, supports a conducting surface.

As an example of the practice of my invention,

Fig. 1 illustrates an original metallic pattern or metal coated patternI which may be of any desired shape consistent with the practicabilityof providing an electrodeposited bodyof iron therefrom. Such a patternmay represent an original engraved article containing intricate designs.The surface of the pattern from which the electrodeposited body of ironis to be formed is cleaned and a thin layer of copper 2, as shown inFig. 2, is deposited thereon. This layer of copper should be relativelythin, and it is essential that the copper be electrodeposited thereon,as distinguished from a deposit formed by immersion of 1 the metalpattern in a bath of copper salts. A thin layer of copper is required sothat minute details on the pattern will not be substantially varied.Also, application of the copper by elec trodeposition is esential toobtain the proper degree of adhesion between the metal pattern and thedeposited copper.

Directly against the copper surface is provided a layer of metallicsilver 3, as shown in Fig. 3. This layer of silver is deposited in animmersion operation, that is by displacement, as distinguished fromelectrodeposition. A typical solution for they silver bath is a solutioncontaining five ounces of silver cyanide per gallon of water.

A silver deposit may be formed by either immersbe electroformed againstthe layer of metallic silver. During this operation a sufficient degreeof adhesion between the copper layer and the silver layer is formed toprevent any of the electrolyte from seeping in between the separationlayers. This is an essential requirement, as the presence of anyelectrolyte between the separation layers will destroy the detail formedin the electrodeposition operation.

Fig. 5 illustrates the method of separating the deposited body of ironfrom the original metallic pattern. As these-portions are separated thecopper layer 2 remains adhered to the metallic pattern I, and the silverlayer 3 adheres to the electrodeposited body of iron I. The fact thatthe metallic silver is not electrolytically deposited on the copperprovides that desired degree of adhesion which permits the layers to besubsequently separated. While some form of electronic action takes placein the immersion deposit of the silver, it is to be understood thatreference to electrodepositing as disti uished from immersion depositionis intended to signify that extraneous electrical energy is required inthe electrodeposition operation, whereas no source of outside electricalenergy is utilized in the immersion process.

The layer of silver 3 which remains in adhesion with theelectrodeposited body of iron may be retained on the electrodepositediron as an integral part thereof. As the layer of silver 3 is firmlybonded to the deposited iron, it provides a bright finish on thetransferred portion of the deposited iron and also protects the surfacefrom oxidation.

While I have shown a preferred method of practicing the invention, it isto be understood that it may be otherwise practiced, as indicated by thescope of the appended claims.

' an iron matrix which consists in electro-plating the mold surface ofthe matrix with copper, coating the copper with a thin layer of silverdeposited by displacement, electro-depositing a thick layer of iron onthe silver and separating the electro-deposited iron with the silverlayer from the copper surface.

' ARTHUR W. GRANT.

